Film-Tech Forum ARCHIVE: Potts Platter Motor Wiring Question

This is topic Potts Platter Motor Wiring Question in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Randy Bowden (Member # 587) on 03-09-2006, 05:36 PM:

This is a question in regards to the old style potts/super platter motors. I'm talking about the ones with the toggle switch on the motor. There are 2 resistors inside this motor, can someone explain the purpose of the 10 ohm resistor that wires across the payout and rewind terminals of the toggle switch? I now have 2 good working motors as a result of removing this resistor, it was basically causing a short. Is there any detriment to permanently removing it?

Posted by John Eickhof (Member # 323) on 03-09-2006, 06:00 PM:

They will not work properly when in use..the resistor is a voltage drop to slightly slow the motor on pay out otherwise the voltage from the variac would be equal going to both the feed (payout)and the take up motor, Because there are usually several wraps of film missing due to what is feeding through the projector, the actual circumference on each platter is different, thus the feed out must be slower than the take up, both platters do not operate at the same speed. So, without the voltage drop, over feeding and erratic feeding will occur. The second resistor is to prevent overheating and overspeed of the motor when building up (make up) film. Other platters have fully electronic speed controls on each motor that replace this simple type of system. I recommend keeping the resistors in!

Posted by Monte L Fullmer (Member # 2797) on 03-10-2006, 03:36 AM:

True, as you notice that the resistors are not in the MUT's motor since it needs the RPM torque to spin that big pulley on the dogged shaft.

Yeppers, keep those resistors in, as John says. Ever seen a platter really take off without any resistance? Loves to throw prints like nobody's business.

..then you got that diode mounted in the motor can as well - to cut the full wave 60hz AC to a pulsating DC reducing that field for less torque and smoother startups.

Posted by Robert Burtcher (Member # 3227) on 03-10-2006, 05:18 AM:

If the resistor is causing a short, replace it. If you can't for whatever reason get one from the manufacturer, Radio Shack or another equivalent electronics parts supplier should be able to get you what you need.

Posted by Louis Bornwasser (Member # 3063) on 03-10-2006, 06:30 AM:

Sadly Radio Shack in most stores has done away with parts. especially large parts. It is easy to obtain any Potts/Strong part. Louis